Samir Manjiyani

Mohammed Salman Khan

Add your custom CSS or javascript/jquery using “Custom WP CSS & JS” plugin to any theme without creating any extra CSS or JS files.
Benefits of Plugin 
* Easy to use. 
* Option to select placement (header or footer) to insert your custom JS. 
* Built with Syntax Code Highlighter. 
* Option to add custom CSS for WP Dashboard.
For Syntax Code Highlighter credits goes to <a href="https://codemirror.net/5/" rel="nofollow ugc">codemirror.net</a>

Custom WP CSS & JS

otimo

A lightweight plugin to add custom CSS, JS/Javascript to any theme. This plugin also gives you an ability to insert JS in header or footer.

Paris Holley

This plugin is meant to be a drop-in to your wordpress installation with no additional configuration. The goals/features of this plugin are:
<ul>
<li>Load javascript files in an asynchronous manner to improve time to DomReady/OnLoad</li>
<li>Use existing wordpress APIs for backwards compatability and prevent coupling to this plugin</li>
<li>Leverage dependency model wordpress provides for assets to improve loading performance</li>
</ul>
Please submit bugs or contributions to the github location and not here on wordpress’ system:
https://github.com/parisholley/wordpress-asynchronous-javascript/
SEO: async js, asynchronous js, async javascript
<h3>Incompatibility</h3>
This plugin will not work out the box with the following plugins (unless they are modified to support asynchronous loading).
<ul>
<li>Jetpack by WordPress.com (social plugin)</li>
<li>WP Most Popular</li>
</ul>

Asynchronous Javascript

Improve page load performance by asynchronously loading javascript using head.js

Custom WP CSS & JS vs Asynchronous Javascript